D. Edmondson - Academia.edu (original) (raw)

Papers by D. Edmondson

Research paper thumbnail of Mechanism of the reductive activation of succinate dehydrogenase

Journal of Biological Chemistry, 1975

When succinate dehydrogenase contains oxalacetate in firmly bound form, activity cannot be expres... more When succinate dehydrogenase contains oxalacetate in firmly bound form, activity cannot be expressed without special pretreatment ("activation") of the enzyme. Reduction of the enzyme results in dissociation of oxalacetate and activation of the enzyme. The course of reductive titrations appears the same whether or not the enzyme contains oxalacetate, and complete reduction as monitored by bleaching of chromophoric groups requires the incorporation of 6 to 7 reducing equivalents in either case. The stoichiometry is that expected from the non-heme iron and flavin content of the enzyme. Activation of the enzyme during reductive titrations occurs predominantly with the incorporation of the second pair of electrons, while determination of activation levels at various poised potentials shows that the group involved is reduced with the uptake of 2 H+ and 2 e-. These characteristics are consistent with titration of the flavin moiety rather than non-heme iron groups. Thus it appears that activation is concurrent with the reduction of flavin to the hydroquinone form. From the measured half-reduction potential for activation, that of the flavin in an oxalacetate-free enzyme has been estimated at-90 to-60 mv at pH 7.

Research paper thumbnail of The Resolution of Active and Inactive Xanthine Oxidase by Affinity Chromatography

Journal of Biological Chemistry, 1972

Preparation of Allopurinol Analog Used in Sepharose Derivatixation 3-(l-H-Pyrazolo(3,~)pyrimidin-... more Preparation of Allopurinol Analog Used in Sepharose Derivatixation 3-(l-H-Pyrazolo(3,~)pyrimidin-4-ylamino)-l-propanol (I)-The compound was prepared by an adaptation of the procedure of Robins (14). A;, N-Dimethylaniline (60 ml, 0.48 mole) was 1.597 This is an Open Access article under the CC BY license. 1.59s Resolution oj Xanthe Oxiclase bz~ ilfinity Chromatography

Research paper thumbnail of Flavoenzyme Structure and Function: Approaches Using Flavin Analogues

Research paper thumbnail of The FAD Binding Sites of Human Monoamine Oxidases A and B

NeuroToxicology, 2004

The structural details of the interactions of the covalent 8alpha-S-cysteinyl-FAD with the protei... more The structural details of the interactions of the covalent 8alpha-S-cysteinyl-FAD with the protein moiety in monoamine oxidase B (MAO B) based on the MAO B crystal structure are described. The dinucleotide is bound to the protein in an extended conformation with the majority of the bonds to the protein identified as hydrogen bonds with amino acid side chains, amide bonds, and water molecules. Since those amino acids interacting with the FAD are conserved in monoamine oxidase A (MAO A), it is proposed that the FAD binding site in MAO A is quite similar to that in MAO B. The redox-active isoalloxazine ring is buried in the protein without direct access to bulk solvent. An electrostatic interaction is observed between the anionic pyrophosphate moiety and Arg42. The normally flat oxidized flavin ring is in a bent, puckered conformation in the MAO B binding site which is suggested to contribute to its reactivity in catalysis. This structural information is then used to explain previous studies on flavin analog incorporation into either MAO B or into MAO A.

Research paper thumbnail of Biochemical, Structural, and Biological Evaluation of Tranylcypromine Derivatives as Inhibitors of Histone Demethylases LSD1 and LSD2

Journal of the American Chemical Society, 2010

LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological p... more LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

Research paper thumbnail of 8α-Substituted flavins of biological importance

Research paper thumbnail of On the Mechanism of Inactivation of Xanthine Oxidase by Cyanide

Journal of Biological Chemistry, 1970

Research paper thumbnail of Crystal structure of human monoamine oxidase B, a drug target enzyme monotopically inserted into the mitochondrial outer membrane

FEBS Letters, 2004

Monoamine oxidase B (MAO B) is an outer mitochondrial membrane protein that oxidizes arylalkylami... more Monoamine oxidase B (MAO B) is an outer mitochondrial membrane protein that oxidizes arylalkylamine neurotransmitters and has been a valuable drug target for many neurological disorders. The 1.7 A î resolution structure of human MAO B shows the enzyme is dimeric with a C-terminal transmembrane helix protruding from each monomer and anchoring the protein to the membrane. This helix departs perpendicularly from the base of the structure in a di¡erent way with respect to other monotopic membrane proteins. Several apolar loops exposed on the protein surface are located in proximity of the C-terminal helix, providing additional membrane-binding interactions. One of these loops (residues 99^112) also functions in opening and closing the MAO B active site cavity, which suggests that the membrane may have a role in controlling substrate binding. ß

Research paper thumbnail of Structure of human monoamine oxidase B, a drug target for neurological disorders

Acta Crystallographica Section A Foundations of Crystallography, 2002

Monoamine oxidase B (MAO B) is a mitochondrial outermembrane flavoenzyme that is a well-known tar... more Monoamine oxidase B (MAO B) is a mitochondrial outermembrane flavoenzyme that is a well-known target for antidepressant and neuroprotective drugs. We determined the structure of the human enzyme to 3 A resolution. The enzyme binds to the membrane through a C-terminal transmembrane helix and apolar loops located at various positions in the sequence. The electron density shows that pargyline, an analog of the clinically used MAO B inhibitor, deprenyl, binds covalently to the flavin N5 atom. The active site of MAO B consists of a 420 A(3)-hydrophobic substrate cavity interconnected to an entrance cavity of 290 A(3). The recognition site for the substrate amino group is an aromatic cage formed by Tyr 398 and Tyr 435. The structure provides a framework for probing the catalytic mechanism, understanding the differences between the B- and A-monoamine oxidase isoforms and designing specific inhibitors.

Research paper thumbnail of Binding of Rasagiline-Related Inhibitors to Human Monoamine Oxidases:  A Kinetic and Crystallographic Analysis

Journal of Medicinal Chemistry, 2005

Monoamine oxidases A and B (MAO A and B) catalyze the degradation of neurotransmitters and repres... more Monoamine oxidases A and B (MAO A and B) catalyze the degradation of neurotransmitters and represent drug targets for the treatment of neurodegenerative disorders. Rasagiline is an irreversible, MAO B-selective inhibitor that has been approved as a novel anti-Parkinson's drug. In this study, we investigate the inhibition of recombinant human MAO A and MAO B by several rasagiline analogues. Different substituents added onto the rasagiline scaffold alter the binding affinity depending on the position on the aminoindan ring and on the size of the substituent. Compounds with a hydroxyl group on either the C4 or the C6 atom inhibit both isozymes, whereas a bulkier substituent such as a carbamate is tolerated only at the C4 position. The 1.7 A crystal structure of MAO B in complex with 4-(N-methyl-N-ethyl-carbamoyloxy)-N-methyl-N-propargyl-1(R)-aminoindan shows that the binding mode is similar to that of rasagiline with the carbamate moiety occupying the entrance cavity space. 1(R)-Aminoindan, the major metabolic product of rasagiline, and its analogues reversibly inhibit both MAO A and MAO B. The crystal structure of N-methyl-1(R)-aminoindan bound to MAO B shows that its aminoindan ring adopts a different orientation compared to that of rasagiline.

Research paper thumbnail of Insights into the mode of inhibition of human mitochondrial monoamine oxidase B from high-resolution crystal structures

Proceedings of the National Academy of Sciences, 2003

Monoamine oxidase B (MAO-B) is an outer mitochondrial membrane-bound enzyme that catalyzes the ox... more Monoamine oxidase B (MAO-B) is an outer mitochondrial membrane-bound enzyme that catalyzes the oxidative deamination of arylalkylamine neurotransmitters and has been a target for a number of clinically used drug inhibitors. The 1.7-Å structure of the reversible isatin-MAO-B complex has been determined; it forms a basis for the interpretation of the enzyme's structure when bound to either reversible or irreversible inhibitors. 1,4-Diphenyl-2-butene is found to be a reversible MAO-B inhibitor, which occupies both the entrance and substrate cavity space in the enzyme. Comparison of these two structures identifies Ile-199 as a ''gate'' between the two cavities. Rotation of the side chain allows for either separation or fusion of the two cavities.

Research paper thumbnail of Biochemical, Structural, and Biological Evaluation of Tranylcypromine Derivatives as Inhibitors of Histone Demethylases LSD1 and LSD2

Journal of the American Chemical Society, 2010

LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological p... more LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

Research paper thumbnail of Inactivation of Purified Human Recombinant Monoamine Oxidases A and B by Rasagiline and Its Analogues

Journal of Medicinal Chemistry, 2004

The inactivation of purified human recombinant monoamine oxidases (MAO) A and B by rasagiline [N-... more The inactivation of purified human recombinant monoamine oxidases (MAO) A and B by rasagiline [N-propargyl-1(R)-aminoindan] and four of its analogues [N-propargyl-1(S)-aminoindan (S-PAI), 6-hydroxy-N-propargyl-1(R)-aminoindan (R-HPAI), N-methyl-N-propargyl-1(R)-aminoindan (R-MPAI), and 6-(N-methyl-N-ethyl carbamoyloxy)-N-propargyl-1(R)-aminoindan (R-CPAI)] has been investigated. All compounds tested, with the exception of R-CPAI, form stoichiometric N(5) flavocyanine adducts with the FAD moiety of either enzyme. No H 2 O 2 is produced during either MAO A or MAO B inactivation, which demonstrates that covalent addition occurs in a single turnover. Rasagiline has the highest specificity for MAO B, as demonstrated by a 100-fold higher inhibition potency (k inact /K i ) compared to MAO A, with the remaining compounds exhibiting lower isozyme specificities. MAO B and MAO A are more selective for the R-enantiomer (rasagiline) compared to the S-enantiomer (S-PAI) by 2500-fold and 17-fold, respectively. Differences in UV/vis and CD spectral data of the complexes of the studied compounds with both MAO A and MAO B are interpreted in light of crystallographic data of complexes of MAO B with rasagiline and its analogues (Binda, C.; et al.

Research paper thumbnail of Biochemical, Structural, and Biological Evaluation of Tranylcypromine Derivatives as Inhibitors of Histone Demethylases LSD1 and LSD2

Journal of the American Chemical Society, 2010

LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological p... more LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

Research paper thumbnail of Dual role of FMN in flavodoxin function: Electron transfer cofactor and modulation of the protein–protein interaction surface

Biochimica Et Biophysica Acta-bioenergetics, 2010

Flavodoxin (Fld) replaces Ferredoxin (Fd) as electron carrier from Photosystem I (PSI) to Ferredo... more Flavodoxin (Fld) replaces Ferredoxin (Fd) as electron carrier from Photosystem I (PSI) to Ferredoxin-NADP+ reductase (FNR). A number of Anabaena Fld (AnFld) variants with replacements at the interaction surface with FNR and PSI indicated that neither polar nor hydrophobic residues resulted critical for the interactions, particularly with FNR. This suggests that the solvent exposed benzenoid surface of the Fld FMN

Research paper thumbnail of Mechanism of the reductive activation of succinate dehydrogenase

Journal of Biological Chemistry, 1975

When succinate dehydrogenase contains oxalacetate in firmly bound form, activity cannot be expres... more When succinate dehydrogenase contains oxalacetate in firmly bound form, activity cannot be expressed without special pretreatment ("activation") of the enzyme. Reduction of the enzyme results in dissociation of oxalacetate and activation of the enzyme. The course of reductive titrations appears the same whether or not the enzyme contains oxalacetate, and complete reduction as monitored by bleaching of chromophoric groups requires the incorporation of 6 to 7 reducing equivalents in either case. The stoichiometry is that expected from the non-heme iron and flavin content of the enzyme. Activation of the enzyme during reductive titrations occurs predominantly with the incorporation of the second pair of electrons, while determination of activation levels at various poised potentials shows that the group involved is reduced with the uptake of 2 H+ and 2 e-. These characteristics are consistent with titration of the flavin moiety rather than non-heme iron groups. Thus it appears that activation is concurrent with the reduction of flavin to the hydroquinone form. From the measured half-reduction potential for activation, that of the flavin in an oxalacetate-free enzyme has been estimated at-90 to-60 mv at pH 7.

Research paper thumbnail of The Resolution of Active and Inactive Xanthine Oxidase by Affinity Chromatography

Journal of Biological Chemistry, 1972

Preparation of Allopurinol Analog Used in Sepharose Derivatixation 3-(l-H-Pyrazolo(3,~)pyrimidin-... more Preparation of Allopurinol Analog Used in Sepharose Derivatixation 3-(l-H-Pyrazolo(3,~)pyrimidin-4-ylamino)-l-propanol (I)-The compound was prepared by an adaptation of the procedure of Robins (14). A;, N-Dimethylaniline (60 ml, 0.48 mole) was 1.597 This is an Open Access article under the CC BY license. 1.59s Resolution oj Xanthe Oxiclase bz~ ilfinity Chromatography

Research paper thumbnail of Flavoenzyme Structure and Function: Approaches Using Flavin Analogues

Research paper thumbnail of The FAD Binding Sites of Human Monoamine Oxidases A and B

NeuroToxicology, 2004

The structural details of the interactions of the covalent 8alpha-S-cysteinyl-FAD with the protei... more The structural details of the interactions of the covalent 8alpha-S-cysteinyl-FAD with the protein moiety in monoamine oxidase B (MAO B) based on the MAO B crystal structure are described. The dinucleotide is bound to the protein in an extended conformation with the majority of the bonds to the protein identified as hydrogen bonds with amino acid side chains, amide bonds, and water molecules. Since those amino acids interacting with the FAD are conserved in monoamine oxidase A (MAO A), it is proposed that the FAD binding site in MAO A is quite similar to that in MAO B. The redox-active isoalloxazine ring is buried in the protein without direct access to bulk solvent. An electrostatic interaction is observed between the anionic pyrophosphate moiety and Arg42. The normally flat oxidized flavin ring is in a bent, puckered conformation in the MAO B binding site which is suggested to contribute to its reactivity in catalysis. This structural information is then used to explain previous studies on flavin analog incorporation into either MAO B or into MAO A.

Research paper thumbnail of Biochemical, Structural, and Biological Evaluation of Tranylcypromine Derivatives as Inhibitors of Histone Demethylases LSD1 and LSD2

Journal of the American Chemical Society, 2010

LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological p... more LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

Research paper thumbnail of 8α-Substituted flavins of biological importance

Research paper thumbnail of On the Mechanism of Inactivation of Xanthine Oxidase by Cyanide

Journal of Biological Chemistry, 1970

Research paper thumbnail of Crystal structure of human monoamine oxidase B, a drug target enzyme monotopically inserted into the mitochondrial outer membrane

FEBS Letters, 2004

Monoamine oxidase B (MAO B) is an outer mitochondrial membrane protein that oxidizes arylalkylami... more Monoamine oxidase B (MAO B) is an outer mitochondrial membrane protein that oxidizes arylalkylamine neurotransmitters and has been a valuable drug target for many neurological disorders. The 1.7 A î resolution structure of human MAO B shows the enzyme is dimeric with a C-terminal transmembrane helix protruding from each monomer and anchoring the protein to the membrane. This helix departs perpendicularly from the base of the structure in a di¡erent way with respect to other monotopic membrane proteins. Several apolar loops exposed on the protein surface are located in proximity of the C-terminal helix, providing additional membrane-binding interactions. One of these loops (residues 99^112) also functions in opening and closing the MAO B active site cavity, which suggests that the membrane may have a role in controlling substrate binding. ß

Research paper thumbnail of Structure of human monoamine oxidase B, a drug target for neurological disorders

Acta Crystallographica Section A Foundations of Crystallography, 2002

Monoamine oxidase B (MAO B) is a mitochondrial outermembrane flavoenzyme that is a well-known tar... more Monoamine oxidase B (MAO B) is a mitochondrial outermembrane flavoenzyme that is a well-known target for antidepressant and neuroprotective drugs. We determined the structure of the human enzyme to 3 A resolution. The enzyme binds to the membrane through a C-terminal transmembrane helix and apolar loops located at various positions in the sequence. The electron density shows that pargyline, an analog of the clinically used MAO B inhibitor, deprenyl, binds covalently to the flavin N5 atom. The active site of MAO B consists of a 420 A(3)-hydrophobic substrate cavity interconnected to an entrance cavity of 290 A(3). The recognition site for the substrate amino group is an aromatic cage formed by Tyr 398 and Tyr 435. The structure provides a framework for probing the catalytic mechanism, understanding the differences between the B- and A-monoamine oxidase isoforms and designing specific inhibitors.

Research paper thumbnail of Binding of Rasagiline-Related Inhibitors to Human Monoamine Oxidases:  A Kinetic and Crystallographic Analysis

Journal of Medicinal Chemistry, 2005

Monoamine oxidases A and B (MAO A and B) catalyze the degradation of neurotransmitters and repres... more Monoamine oxidases A and B (MAO A and B) catalyze the degradation of neurotransmitters and represent drug targets for the treatment of neurodegenerative disorders. Rasagiline is an irreversible, MAO B-selective inhibitor that has been approved as a novel anti-Parkinson's drug. In this study, we investigate the inhibition of recombinant human MAO A and MAO B by several rasagiline analogues. Different substituents added onto the rasagiline scaffold alter the binding affinity depending on the position on the aminoindan ring and on the size of the substituent. Compounds with a hydroxyl group on either the C4 or the C6 atom inhibit both isozymes, whereas a bulkier substituent such as a carbamate is tolerated only at the C4 position. The 1.7 A crystal structure of MAO B in complex with 4-(N-methyl-N-ethyl-carbamoyloxy)-N-methyl-N-propargyl-1(R)-aminoindan shows that the binding mode is similar to that of rasagiline with the carbamate moiety occupying the entrance cavity space. 1(R)-Aminoindan, the major metabolic product of rasagiline, and its analogues reversibly inhibit both MAO A and MAO B. The crystal structure of N-methyl-1(R)-aminoindan bound to MAO B shows that its aminoindan ring adopts a different orientation compared to that of rasagiline.

Research paper thumbnail of Insights into the mode of inhibition of human mitochondrial monoamine oxidase B from high-resolution crystal structures

Proceedings of the National Academy of Sciences, 2003

Monoamine oxidase B (MAO-B) is an outer mitochondrial membrane-bound enzyme that catalyzes the ox... more Monoamine oxidase B (MAO-B) is an outer mitochondrial membrane-bound enzyme that catalyzes the oxidative deamination of arylalkylamine neurotransmitters and has been a target for a number of clinically used drug inhibitors. The 1.7-Å structure of the reversible isatin-MAO-B complex has been determined; it forms a basis for the interpretation of the enzyme's structure when bound to either reversible or irreversible inhibitors. 1,4-Diphenyl-2-butene is found to be a reversible MAO-B inhibitor, which occupies both the entrance and substrate cavity space in the enzyme. Comparison of these two structures identifies Ile-199 as a ''gate'' between the two cavities. Rotation of the side chain allows for either separation or fusion of the two cavities.

Research paper thumbnail of Biochemical, Structural, and Biological Evaluation of Tranylcypromine Derivatives as Inhibitors of Histone Demethylases LSD1 and LSD2

Journal of the American Chemical Society, 2010

LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological p... more LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

Research paper thumbnail of Inactivation of Purified Human Recombinant Monoamine Oxidases A and B by Rasagiline and Its Analogues

Journal of Medicinal Chemistry, 2004

The inactivation of purified human recombinant monoamine oxidases (MAO) A and B by rasagiline [N-... more The inactivation of purified human recombinant monoamine oxidases (MAO) A and B by rasagiline [N-propargyl-1(R)-aminoindan] and four of its analogues [N-propargyl-1(S)-aminoindan (S-PAI), 6-hydroxy-N-propargyl-1(R)-aminoindan (R-HPAI), N-methyl-N-propargyl-1(R)-aminoindan (R-MPAI), and 6-(N-methyl-N-ethyl carbamoyloxy)-N-propargyl-1(R)-aminoindan (R-CPAI)] has been investigated. All compounds tested, with the exception of R-CPAI, form stoichiometric N(5) flavocyanine adducts with the FAD moiety of either enzyme. No H 2 O 2 is produced during either MAO A or MAO B inactivation, which demonstrates that covalent addition occurs in a single turnover. Rasagiline has the highest specificity for MAO B, as demonstrated by a 100-fold higher inhibition potency (k inact /K i ) compared to MAO A, with the remaining compounds exhibiting lower isozyme specificities. MAO B and MAO A are more selective for the R-enantiomer (rasagiline) compared to the S-enantiomer (S-PAI) by 2500-fold and 17-fold, respectively. Differences in UV/vis and CD spectral data of the complexes of the studied compounds with both MAO A and MAO B are interpreted in light of crystallographic data of complexes of MAO B with rasagiline and its analogues (Binda, C.; et al.

Research paper thumbnail of Biochemical, Structural, and Biological Evaluation of Tranylcypromine Derivatives as Inhibitors of Histone Demethylases LSD1 and LSD2

Journal of the American Chemical Society, 2010

LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological p... more LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

Research paper thumbnail of Dual role of FMN in flavodoxin function: Electron transfer cofactor and modulation of the protein–protein interaction surface

Biochimica Et Biophysica Acta-bioenergetics, 2010

Flavodoxin (Fld) replaces Ferredoxin (Fd) as electron carrier from Photosystem I (PSI) to Ferredo... more Flavodoxin (Fld) replaces Ferredoxin (Fd) as electron carrier from Photosystem I (PSI) to Ferredoxin-NADP+ reductase (FNR). A number of Anabaena Fld (AnFld) variants with replacements at the interaction surface with FNR and PSI indicated that neither polar nor hydrophobic residues resulted critical for the interactions, particularly with FNR. This suggests that the solvent exposed benzenoid surface of the Fld FMN